The invention relates to a control valve and finds particular application in the control of exhaust gas recirculation (EGR) valves or in the control of idle speed devices for internal combustion engines.
Control of exhaust gas recirculation in internal combustion engines has been utilized to reduce the amount of harmful oxides of nitrogen (NOX) components in such exhaust. In the prior art, some devices are controlled by various engine parameters and cooperate with such engines to recirculate exhaust gases to reduce NOX components in the exhaust gases. However, these earlier devices are almost universally operable by a diaphragm operator responsive to a vacuum or pressure differential signal. Such a signal is often derived from the engine manifold vacuum. This interruption of the manifold vacuum interferes with the fuel-air mixture to the internal combustion chambers. Such interference in the fuel-air balance leads to further disturbance in the equilibrium or stoichiometry of the combustion mixture for such engines. NOX output in the exhaust may be reduced by not disturbing the vacuum signal. The present invention provides a positive control for valves used in EGR system without disturbing the air-fuel mixture or bleeding-off the manifold vacuum. Such control means also are useful in the control of idle speed circuits. U.S. Pat. No. 3,977,375 (Laprade et al) is illustrative of the prior art wherein EGR valves are controlled by a vacuum signal wherein an exhaust gas recirculation valve is controlled in response to a signal in the exhaust pipe. Such signal is delivered from a sensor to an electromagnetic valve to control the vacuum from a proportioning device to a diaphragm biased by a spring. The diaphragm is connected to an EGR valve to thereby allow recirculation from said exhaust to the inlet manifold. This type of vacuum control is prevalent throughout the prior art. That is, the control of a vacuum signal to a diaphragm operator to modulate the EGR valve.
An alternative control for an EGR system is illustrated in U.S. Pat. No. 4,175,522 (Kawamura et al) wherein a cam operated valve and a expansion manifold system are connected such that exhaust gas is expanded into the manifold through one of the cam operator valves and thereafter into the auxiliary combustion chamber of a cylinder via a second open cam operated valve. These cam operated valves are hydraulically actuated through a solenoid control valve. This solenoid controller is energized under high load conditions to establish a hydraulic path which returns oil to the sump and under this high load condition the cam operated valves do not open.
U.S. Pat. No. 4,233,946 (Yorioka et al) describes an exhaust gas recirculation system for an internal combustion engine wherein a variable restriction connection is provided between an intake pipe and a control valve through a cam actuator. In this situation a throttle or constriction in an intake pipe is connected by a link to a cam so that the opening area of a variable constriction has a definite relationship to a throttle valve. This link and cam connection is moved to vary the flow to a diaphragm operated EGR valve; thus this is a controlled valve, operable to again control a diaphragm operator of an EGR valve. This arrangement provides no direct link to such an EGR valve.
U.S. Pat. No. 4,411,242 (Igashira et al) teaches a method for controlling an EGR valve in an internal combustion engine based upon detection of the fuel amount by a sensor in line with the predetermined EGR rate equation. The controller as illustrated in the figure is a pressure controlling valve 6 which is shown as an electromagnetic valve or solenoid valve.
According to the present invention there is provided a direct drive to a valve independent of manifold vacuum to thereby avoid disturbance of the fuel/air mixture to the engine while still providing a means to introduce exhaust gas to reduce the amount of harmful NOX discharged to the atmosphere. The valve is responsive to a signal from a sensor which may be responsive to one or more engine operating parameters such as oxygen content, engine revolutions, vehicle speed, exhaust gas pressure or some other major parameter. The present invention provides a motor operator and a cam and stem arrangement to control flow past a valve pintle.